From the course: Fundamentals of Data Transformation for Data Engineering

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Advanced joins

Advanced joins - SQL Tutorial

From the course: Fundamentals of Data Transformation for Data Engineering

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Advanced joins

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- [Instructor] So now that we've discussed some advanced methods of filtering data, it's time to talk about how we can join data in some advanced, or maybe uncommon ways. And there are two main things I want to cover here. First is going to be how to use a cross join, and second, the importance of self joins. So joins can be really useful, actually just bringing data onto itself can be really useful for generating combinations of data, but then also simulating events or interactions, and I'll show you a few examples of what we mean here. But the one thing that's important to remember is that cross joins join every record in one column to every record in another. And so the note I have here, right, if you cross join two 1000-record tables, two 1000-record rows, you'll produce a million rows in the resulting dataset. So it's important to consider magnitude when you're doing cross joins. If we're looking at something like national parks, it's okay, because there are only like 60 or so…

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